Reset textcase in speak/speak_active

Originally, textcase was reset in scriptclass::translate_dialogue(),
which is called inside the `text` script command. However, this didn't
really work with the new on-the-fly text box translation system, and
that function is gone now, so I removed that and kind of forgot about
it.

Of course, this now causes a regression. Namely, that the text boxes
after the VVVVVV-Man sequence in the Secret Lab entrance cutscene are
not translated.

I can't reset the text case in `text`, as the scripts assume that they
can set the text case before `text`. So the next best thing is to reset
it in speak/speak_active.

desktop_version/src/Script.cpp

@@ -811,6 +811,8 @@ void scriptclass::run(void)
                     graphics.textboxbuttons();
                 }
                 textbuttons = false;
+
+                textcase = 1;
             }
             else if (words[0] == "endtext")
             {